Solar System Log by Andrew Wilson, published 1987 by Jane's Publishing Co. Ltd.

The Pioneer Venus project comprised two spacecraft to explore the atmosphere and surface of Venus. Both spacecraft used a basic cylindrical bus.

Pioneer Venus 1, the orbiter, was designed to spend an extended period in orbit around Venus mapping the surface using a radar package.

The orbiter entered an elliptical orbit around Venus on 4 December 1978 after a 6.5-month journey. The initial orbital period was 23.4 hours, which was altered within two orbits to the desired 24 hours - a maneuver that would allow the
orbit's high and low points (about 150 kilometers) to occur at the same time each Earth day.

Data from the radar mapper allowed scientists to produce a topographical map of most of the Venusian surface between 73° north and 63° south latitude at a resolution of 75 kilometers.

The data indicated that Venus was much smoother and more spherical than Earth. The orbiter identified the highest point on Venus as Maxwell Montes, which rises 10.8 kilometers above the mean surface. Infrared observations revealed a clearing in the planet's atmosphere over the north pole. In addition, ultraviolet light photos showed dark markings that covered the clouds in the visible hemisphere.

Cameras also detected almost continuous lightning activity in the atmosphere. The spacecraft confirmed that Venus has little, if any, magnetic field. Although the mapping radar was switched off on 19 March 1981, it was reactivated again in 1991, thirteen years after launch, to explore the previously inaccessible southern portions of the planet.

In May 1992, Pioneer Venus 1 began the final phase of its mission, maintaining its periapsis between 150 and 250 kilometers until propellant depletion. The last transmission was received at 19:22 UT on 8 October 1992, as its decaying orbit no longer permitted communications. The spacecraft burned in the atmosphere soon after, ending a successful fourteen-year mission that was planned to last only eight months.

Key Dates

20 May 1978: Launch

4 Dec 1978: Venus Orbit Insertion

Status: Successful

Fast Facts

Pioneer Venus 1 was the first spacecraft to map the surface of Venus (right).

Though it found Venus to be generally smoother than Earth, it found a mountain 2 km (about one mile) higher than Mt. Everest and a canyon about 1.1 km (about 2/3 of a mile) deeper than the Grand Canyon.

The International Astronomical Union named almost all of the features discovered by Pioneer Venus 1 and subsequent missions after historical or mythological women.

People Spotlight

Charles Hall"Charlie Hall's Pioneer 10 craft may be billions of miles from Earth, but his spirit will always be with us at NASA."